
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21609.43    170.5826    22424.31    21275.07    21943.79
experime |  17,281    22038.81    175.6214     23086.7    21694.58    22383.05
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -429.3801    244.8291               -909.2531    50.49298
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =  -1.7538
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0397         Pr(|T| > |t|) = 0.0795          Pr(T > t) = 0.9603
